Many flat panel displays (FPDs) such as liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), electroluminescences (ELs), light-emitting displays (LEDs), and organic LEDs (OLEDs) are commercially available. During a process of manufacturing a FPD, a thin-film transistor (TFT) array testing process may be performed. A TFT array is an aggregate of pixel electrodes of FPDs (e.g., LCDs) and switching devices configured to select the pixel electrodes. Various defects are likely to occur during the manufacturing process. The TFT array testing process may be broadly divided into a contact process of directly testing a TFT array for defects by using probe and a non-contact process of testing a TFT array for defects by using dislocation contrast or a voltage image method.